R1:fc9bbb9949f8

Workboard: fix regression caused by tags= prefiller

Summary:
This change fixes a regression introduced here:

rP5e2b3677157889104a7e540d7772a04f13164037

Thank you to the user @dadalha for auditing that commit
and sharing a stack trace to easily fix the issue.

In short, if you see this exception you are affected:

```
EXCEPTION: (InvalidArgumentException)
Value provided to "replaceQueryParam()" for key "tags" is NULL.
Use "removeQueryParam()" to remove a query parameter.
at…